Pandemic influenza: an evolving challenge

22 May 2018

100 years after the 1918 Influenza Pandemic known as "Spanish flu" ravaged the globe, what have we learned?

New Contributed Photographs Collection/Otis Historical Archives/National Museum of Health and Medicine


The Pandemic Influenza of 1918: Remembering the flu that killed millions around the globe

2018 marks the 100th anniversary of one of the largest public health crises in modern history, the 1918 influenza pandemic known colloquially as “Spanish flu.” The intensity and speed with which it struck were almost unimaginable – infecting one-third of the Earth’s population, which at the time was about 500 million people. By the time it subsided in 1920, tens of millions people are thought to have died.

There was nothing “Spanish” about the influenza epidemic of 1918, which began during World War I and affected countries around the globe. The cost in human life eclipsed that of World War I: more American troops, for instance, died from flu than they did in the battlefield.


A modern disease

Although influenza has been with humankind for millenia, the virulence and global spread is in many respects a function of modern times. Urbanization, mass migration, global transport and trade, and overcrowding accelerate the spread of pandemics, which ignore national borders, social class, economic status, and even age. The 1918 Pandemic, for instance, was unusually fatal in the 20-to-40 age group. Like many other diseases, influenza pandemics impact the poor the hardest. At the same time, they disrupt the economy and basic social functions like school and other mass gatherings.


From global problem to global approach

In the wake of the devastation of the Spanish flu, the world came together to develop unprecedented scientific collaborations to take on future pandemics. In 1947, the WHO Interim Committee of the United Nations established a Global Influenza Programme to track the changes in the virus. In 1952 the Global Influenza Surveillance Network was officially launched, with 26 collaborating laboratories around the world. Today, renamed the Global Influenza Surveillance and Response System (GISRS), the network comprises 153 institutions in 114 countries. The sharing of viruses and data among different nations is a critical tool in global efforts against both seasonal flu and pandemic influenza.


Predictably unpredictable

Pandemic Influenza outbreaks have been predictably unpredictable in the years since 1918 – but always global, and needing a global response. One million people around the world died in a 1957 outbreak which started in China but spread globally. In 1968, another outbreak took 1 to 3 million lives. In 2003, A(H5N1) or so-called Avian Influenza highlighted how the virus could pass from animals to humans, but it did not reach the pandemic stage because it did not pass from human to human. The 2009 “Swine flu” A(H1N1) pandemic, started in Mexico and spread to over 214 countries and overseas territories or communities. The world was lucky: it turned out to be even milder than some seasonal epidemics. Researchers are always on the lookout, though, because the next outbreak could be far worse.


Preparing for the next pandemic with new tools, new partnerships

WHO is working closely with Ministries of Health, regional and national influenza research and surveillance centres, and other stakeholders to develop a multi-layered approach to preparing for and responding to both seasonal flu outbreaks and pandemics. Specific WHO programmes include the Global Influenza Surveillance and Response System (GISRS), and the Pandemic Influenza Preparedness Framework, which helps developing countries access vaccines, antivirals, and diagnostics to both prepare for and manage pandemics.

WHO and partners are developing a “Global Influenza Strategy” to be launched in 2018. Aligned with the general programme of work 2019-2023 (GPW13), the new strategy will support WHO Member States in developing seasonal influenza prevention and control capacities. These national efforts, in turn, will build greater global preparedness for the next pandemic. Globally, the strategy will focus on research and innovation. This will include improved influenza modelling and forecasting, along with the development of new vaccines, including a possible universal influenza vaccine.

This page links all WHO technical and general information on influenza

Pandemic Influenza Preparedness Framework

The PIP Framework brings together Member States, industry, other stakeholders and WHO to implement a global approach to pandemic influenza preparedness and response.

Online courses on pandemic influenza

Every few decades a new, and potentially deadly, influenza virus emerges and spreads worldwide. These events – influenza pandemics – are a threat all countries need to prepare for.